Such an electrosurgical system is known from U.S. Pat. No. 6,074,386 (Goble et al). In this system, the generator forms part of a first unit and the electrode assembly forms part of a second unit, the second unit being detachably connectible to the first unit such that RF power can be conveyed to the electrode assembly. The second unit includes a capacitor the capacitance value of which is indicative of a characteristic of the electrode assembly. The generator includes a sensing circuit having an inductance which, when the first unit is connected to the second unit, forms a resonant circuit the resonant frequency of which depends on the capacitance value. By arranging for this resonant circuit to form part of an oscillator, it is possible to generate an alternating signal the frequency of which is indicative of the above-mentioned characteristic of the electrode assembly and, furthermore, the oscillator output signal is fed to a controller configured to adjust the output of the generator in response to the oscillator signal so as to suit the indicated electrode assembly characteristic. It follows that different electrode assemblies having different characteristics can be provided with capacitors of different capacitance values so that, when an electrode assembly is attached to the generator, the generator is automatically adjusted to deliver the right output for that electrode assembly.